Video of an ILS failure and CRM

[Amish RakeFight]

During my IR training Night X/C, intercepted above and got the wrong gs indication. My CFII knew it, but let me take it until I caught it when I crosschecked altitudes on the plate at the fix. Classic false gs scenario.

Was your descent rate excessive on the VSI? I'm wondering what it actually looks like and how high above the minimum GS int. alt. were you?

It's one of those things you read about but never really experience. I should go out and try it one day.

 

[Learsforsale]

Although not mentioned, intercepting the GS too high can cause excessively high descent rates and lead to false indications.

Has anyone ever encountered this phenomenon?

Its been awhile since my Instrument class but I remember something about false glideslopes that can be encountered above the normal glideslope. IIRC that is one reason that the altitude at FAF on GS is printed on the chart, so you know you are on the correct GS (in case you couldn't figure it out before).

 

[PositionandHold]

Was your descent rate excessive on the VSI? I'm wondering what it actually looks like and how high above the minimum GS int. alt. were you?

It's one of those things you read about but never really experience. I should go out and try it one day.

It's been some time so I don't remember exactly what happened, but I think I got distracted with something and waited too long to descend to the intercept altitude and I reacted by descending (probably steeper than normal) to catch it instead of going missed; and ended up catching what I thought was the GS but what was actually a false GS. In retrospect, going missed would have been the best option right away.

A couple of weeks after getting the ticket, I flew into an airport and was given "bad" vectors to intercept the glideslope, in and out of IMC and runway not in sight. As soon as I was given an intercept hdg and clearance for the approach, I already had full above GS Deflection on the CDI (i.e. needle was all the way down). I could have descended to catch it but why? So I asked for new vectors to re-intercept. Not worth the risk, especially in and out of IMC. If it was clear, I would have taken it fine.

 

[Gorilla]

The VS should be approx 1/2 the GS times 10.

?? Did you mean X 100? Otherwise you're looking at 15 fpm.

V/S is totally dependent upon approach speed. Your rule of thumb will vary, of course, with the type of AC you are flying. At 150 knots in a 737, V/S is going to be 700 or 800 fpm, not 1/2 GS X 100 which would be ~ 150 fpm for a 3 degree slope.

 

[wrxpilot]

?? Did you mean X 100? Otherwise you're looking at 15 fpm.

V/S is totally dependent upon approach speed. Your rule of thumb will vary, of course, with the type of AC you are flying. At 150 knots in a 737, V/S is going to be 700 or 800 fpm, not 1/2 GS X 100 which would be ~ 150 fpm for a 3 degree slope.

He meant GS = groundspeed, not glideslope... So for your example 150/2 = 75; 75x10 = 750 FPM. Just a nomenclature thing, I know you're already aware of the rule. Just thought I'd clear it up for everybody.

 

[CoATP]

false glideslopes will be at multiples of the angle of the "real" one. Usually you will see one at twice the angle (about 6 deg) so descent rate will be x2 (or about 1500 fpm) anything in excess of 600-900 fpm should be suspect.

 

[Morettis]

Had the same thing happen to me after I had an engine lose oil pressure on climbout. I tuned in the ILS and it bounced around a little then showed on glidepath but it was really the glideslope reciever in the plane quit and that's where the needle defaults to. Not so much fun to switch to a localizer approach using a separate vor for your stepdown fixes...

 

[Gorilla]

He meant GS = groundspeed, not glideslope... So for your example 150/2 = 75; 75x10 = 750 FPM. Just a nomenclature thing, I know you're already aware of the rule. Just thought I'd clear it up for everybody.

I stand totally corrected, TY.